Method of laser beam localized-coating

ABSTRACT

A process is disclosed for laser welding sheet metal plates having an anti-corrosion surface layer pre-coat. The plates are arranged one relative to the other in an edge-butting relationship. Using a laser beam having a first beam spot-size, a laser weld joint is formed along the adjacent edges of the sheet metal plates. Subsequent to forming the laser weld joint, a localized anti-corrosion surface layer is formed at least on the laser weld joint. In particular, a laser beam having a second beam spot-size larger than the first beam spot-size is scanned along the laser weld joint. During the scanning, a flow of a powdered anti-corrosion surface layer material is directed toward a portion of the laser weld joint that is being irradiated by the laser beam. The powdered material is melted by the laser beam and forms a layer adhering to the laser weld joint.

FIELD OF THE INVENTION

The present invention relates generally to laser welding in themanufacture of sheet metal components, such as for example automobilecomponents. More particularly, the present invention relates to aprocess and a system for forming a localized anti-corrosion surfacelayer along a laser welded joint (weld bead), subsequent to the laserwelding together of sheet metal plates having an anti-corrosion surfacelayer pre-coat.

BACKGROUND OF THE INVENTION

Automobiles are mass-produced along assembly lines, in which the varioussystems and components that make up an automobile are joined togetherusing human and/or robot controlled tools. Oftentimes, different sheetmetal pieces are joined together in order to form a desired component.For instance, “tailor-welded blanks” are formed by joining together,such as for instance by laser welding, two or more steel blanks ofdifferent compositions and/or different thicknesses. After thewelded-blanks have been cold-pressed, components are obtained havingproperties of mechanical strength, pressability and impact absorptionthat vary within the components themselves.

In order to provide improved corrosion resistance, it is common tofabricate such blanks using coated sheet-metal materials, such as forinstance boron steels with an aluminum-silicon or a zinc pre-coatingsurface layer. Unfortunately, the process of laser welding together thepre-coated sheet metal plates results in the formation of a weld jointthat is devoid of anti-corrosion protection. Over time, exposure towater, road salt, etc. leads to corrosion along the weld joint andconcomitant loss of weld integrity. Loss of weld integrity can lead toseparation of the sheet metal plates along the weld joint, resulting infailure of the entire component.

In addition, for hot-stamped components that are fabricated from boronsteel, such as Usibor material, the disruption of the AlSi layer alongthe weld joint causes scaling along the weld joint during subsequenthot-stamping processing.

The prior art solution to this problem involves applying a primer layerto cover the weld joint, and then painting the component to provide aphysical barrier from the ambient environment. Unfortunately, thecorrosion protection that is provided by the paint layer is inferior tothe original coating since the bonding of the paint layer to the basemetal is weak. In addition, the paint layer may become damaged overtime, allowing water, road salt etc. to come into contact with theunderlying weld joint. This may happen, for instance, if the paint isscratched or chipped, or if the paint is not applied properly in thefirst place and therefore fails to adhere to the underlying material.Further, only the exterior surfaces of many components are painted, andas a result corrosion may occur along the inward-facing surface of theweld joint.

It would therefore be beneficial to provide a process and system thatovercome at least some of the above-mentioned limitations anddisadvantages of the prior art.

SUMMARY OF THE INVENTION

According to an aspect of at least one embodiment of the instantinvention, a process is disclosed for laser welding together sheet metalplates, the sheet metal plates each having an anti-corrosion surfacelayer pre-coat, the process including: arranging the sheet metal platesone relative to the other and such that an edge of one of the plates isadjacent to and in contact with an edge of another one of the plates;using a laser beam having a first beam spot-size, forming a laser weldjoint along the adjacent edges of the sheet metal plates; and subsequentto forming the laser weld joint, forming a localized anti-corrosionsurface layer at least on the laser weld joint, including: scanning alaser beam having a second beam spot-size along the laser weld joint,the second beam spot-size larger than the first beam spot-size; andduring the scanning, providing a flow of a powdered anti-corrosionsurface layer material toward a portion of the laser weld joint that isbeing irradiated by the laser beam, wherein the powdered anti-corrosionsurface layer material is melted by the laser beam and forms a layeradhering to the laser weld joint.

According to an aspect of at least one embodiment of the instantinvention, a process is disclosed for joining together metallic parts,including: joining together a first metallic part and a second metallicpart at a joining region, at least one of the first metallic part andthe second metallic part having an anti-corrosion surface layerpre-coat, and wherein the surface layer pre-coat is disrupted within thejoining region during the joining; and forming a localizedanti-corrosion surface layer within a target area that is at least oneof within the joining region and adjacent to the joining region,including: scanning a laser beam having a predetermined beam spot-sizethrough the target area; and during the scanning, providing a flow of apowdered anti-corrosion surface layer material toward a portion of thetarget area that is being irradiated by the laser beam, wherein thepowdered anti-corrosion surface layer material is melted by the laserbeam and forms a layer adhering to surfaces within the joining region.

According to an aspect of at least one embodiment of the instantinvention, a multi-part side panel for an automobile is disclosed,having: two sheet metal plates, each having an anti-corrosion surfacelayer pre-coat, and being joined together along a laser weld joint; anda localized anti-corrosion surface layer formed at least on the laserweld joint, whereby the localized anti-corrosion surface layer forms abarrier between the laser weld joint and the ambient atmosphere.

According to an aspect of at least one embodiment of the instantinvention, a door ring for an automobile is disclosed, having: two sheetmetal plates, each having an anti-corrosion surface layer pre-coat, andbeing joined together along a laser weld joint; and a localizedanti-corrosion surface layer formed at least along the laser weld joint,whereby the localized anti-corrosion surface layer forms a barrierbetween the laser weld joint and the ambient atmosphere.

According to an aspect of at least one embodiment of the instantinvention, a multi-piece part for an automobile is disclosed, having twosheet metal plates, each having an anti-corrosion surface layerpre-coat, and being joined together along a laser weld joint; and alocalized anti-corrosion surface layer formed at least on the laser weldjoint, whereby the localized anti-corrosion surface layer forms abarrier between the laser weld joint and the ambient atmosphere. Forexample, the multi-piece part is a multi-piece body side for anautomobile or a multi-part side panel for an automobile.

According to an aspect of at least one embodiment of the instantinvention, a system is disclosed for laser-welding together pre-coatedsheet metal plates, comprising: a support for holding a first pre-coatedsheet metal plate in a predetermined orientation relative to a secondpre-coated sheet metal plate, such that an edge of the first plate andan edge of the second plate are disposed adjacent to one another anddefine an interface therebetween; a laser optic assembly in opticalcommunication with a laser source and operable in a first mode forscanning a laser beam having a first beam spot-size along the interfaceand in a second mode for scanning a laser beam having a second beamspot-size larger than the first beam spot-size along the interface; apowder delivery conduit in communication with a source of a powderedanti-corrosion surface layer material and having an outlet end disposedfor directing a flow of the powdered anti-corrosion surface layermaterial toward the interface; and at least one actuator for relativelymoving the laser optic assembly and the outlet end of the powderdelivery conduit relative to the support, wherein the laser beam havingthe first beam spot-size is scanned along the interface in a first passto form a laser weld joint between the first and second plates, andwherein the laser beam having the second beam spot-size is scanned alongthe laser weld joint, and at the same time the powdered anti-corrosionsurface layer material is fed via the powder delivery conduit toward acurrently irradiated portion of the laser weld joint, to form alocalized anti-corrosion surface layer at least on the laser weld joint.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example only, and withreference to the attached drawings, wherein similar reference numeralsdenote similar elements throughout the several views. It should beunderstood that the drawings are not necessarily to scale. In certaininstances, details that are not necessary for an understanding of thedisclosure or that render other details difficult to perceive have beenomitted.

FIG. 1A-1B are simplified perspective diagrams showing a systemaccording to an embodiment of the invention, subsequent to laser weldingtwo pre-coated sheet metal plates together, and during formation of alocalized anti-corrosion surface layer along the laser weld joint.

FIG. 2A shows a localized anti-corrosion surface layer formed on a firstside of a laser weld joint.

FIG. 2B is an enlarged view of a portion of FIG. 2A.

FIG. 3A shows a localized anti-corrosion surface layer formed on asecond side of the laser weld joint, which is opposite the first sideshown in FIG. 2A.

FIG. 3B is an enlarged view of a portion of FIG. 3A.

FIG. 4 is a cross-sectional view taken along the line A-A in FIG. 1, andshowing a localized anti-corrosion surface layer on a laser weld joint.

DETAILED DESCRIPTION OF THE INVENTION

The following description is presented to enable a person skilled in theart to make and use the invention, and is provided in the context of aparticular application and its requirements. Various modifications tothe disclosed embodiments will be readily apparent to those skilled inthe art, and the general principles defined herein may be applied toother embodiments and applications without departing from the scope ofthe invention. Thus, the present invention is not intended to be limitedto the embodiments disclosed, but is to be accorded the widest scopeconsistent with the principles and features disclosed herein.

Referring now to FIG. 1A-1B, shown are simplified perspective diagramsof a system 100 in accordance with an embodiment of the invention. Moreparticularly, system 100 is shown at a time that is subsequent to laserwelding together two pre-coated sheet metal plates 8 and 9, and that isduring the forming of a localized anti-corrosion surface layer 7 alonglaser weld joint 6. Plate 8 includes a substrate 1, which has a pre-coatlayer 3 disposed on both sides thereof. Similarly, plate 9 includes asubstrate 2, which has a pre-coat layer 3 disposed on both side thereof.In the example that is shown in FIG. 1 the substrate 2 is relativelythicker than the substrate 1, but optionally the substrates have thesame thickness. By way of a specific and non-limiting example thesubstrates 1 and 2 are fabricated from boron steels, and may bedissimilar e.g. having different mechanical properties and/or differentalloy compositions. The pre-coat layers 3 are formed in a known manner,such as for instance by dip-coating the substrates 1 and 2 in a bath ofmolten zinc or molten aluminum alloy. It is to be understood that, forsimplicity, the pre-coat layers 3 are depicted in FIG. 1A and FIG. 1B asa single layer. However, in practice the pre-coat layers 3 comprise anintermetallic alloy layer that is in contact with the steel substrate 1or 2, and a metallic alloy layer that is in contact with theintermetallic alloy layer. Typically, the material of the pre-coatlayers 3 has a melting temperature that is much lower than the meltingtemperature of the underlying steel substrate 8 or 9. For instance, analuminum-silicon (AlSi) alloy coating has a melting temperature lowerthan 600° C., compared to about 1500° C. for the steel substrate.

The system 100 includes a laser optic assembly 4, which receives laserlight from a laser source via a fiber (referred to collectively as lasersource 10). The laser optic assembly 4 is operable in a first mode forscanning a laser beam having a first beam spot-size along the interfacebetween adjacent edges of plates 8 and 9, and also in a second mode forscanning a laser beam having a second beam spot-size along the resultingweld joint that is formed at the interface, the second beam spot-sizebeing larger than the first beam spot-size. By way of an example, thelaser optic assembly 4 includes at least a lens, and the fiber of thelaser source 10 is either a single core fiber or a multiple core fiberbundle.

The system 100 also includes a conduit 5 that is in communication with anot illustrated source of powdered anti-corrosion surface layermaterial, and having an outlet end that is disposed for directing a flow11 of powdered anti-corrosion surface layer material toward the laserweld joint 6. Optionally, conduit 5 includes a not illustrated nozzle atan outlet end thereof for controlling delivery of the powderedanti-corrosion surface layer material. A not-illustrated support isprovided for maintaining the plate 8 relative to the plate 9 for beingwelded together along adjacent edges thereof. The system 100 furtherincludes at least one not-illustrated actuator for relatively moving thelaser optic assembly 4 relative to the support. Optionally, the at leastone actuator supports translational movement of the support and/or thelaser optic assembly 4 and/or the conduit 5. Alternatively, the at leastone actuator supports rotational movement of at least a portion of thelaser optic assembly 4, such as for instance a not-illustrated mirrorelement.

A process according to an embodiment of the invention is performed intwo steps, including a laser welding step for joining together theplates 8 and 9 and a protective layer forming step for forming ananti-corrosion layer on at least the weld joint between the plates 8 and9. The laser-welding step includes using the laser optic assembly 4 togenerate a laser beam having a first beam spot-size. The first beamspot-size is selected such that the laser beam causes heating along theadjacent edges of the plates 8 and 9 that is sufficient to melt thematerial of the substrates 1 and 2, thereby forming a weld pool. As thelaser beam is scanned along interface between the plates 8 and 9, acontinuous weld joint 6 is formed. As is apparent to one of skill in theart, the weld joint 6 is devoid of a protective anti-corrosion layer.Further, the laser-welding step disrupts the pre-coat layer 3 adjacentto the laser weld joint 6, thereby exposing the underlying substrate 1,2. The laser weld joint 6 and the regions of exposed substrate 1, 2 aresusceptible to corrosion under the normal operating conditions of anautomobile, and may be the site of component failure at some time in thefuture.

The protective-layer forming step is performed subsequently, in order toimprove corrosion resistance along the laser weld joint 6 and within theregions of exposed substrate 1, 2. The protective-layer forming stepincludes using the laser optic assembly 4 to generate a laser beamhaving a second beam spot-size, wherein the second beam spot-size islarger than the first beam spot-size. As the laser beam is scanned inthe direction indicated by arrow 12, a flow 11 of the powderedanti-corrosion surface layer material is directed toward the laser weldjoint 6, at a location that is currently being irradiated by the laserbeam. The second beam spot-size is selected such that the laser beamcauses heating that is sufficient to melt the powdered anti-corrosionsurface layer material, but not the material of the substrates 1 and 2or the material of the weld joint 6. For example, when the powderedanti-corrosion surface layer material is powdered zinc the heatingachieves a temperature of about 400° C., and when the powderedanti-corrosion surface layer material is powdered AlSi the heatingachieves a temperature of about 600° C. After the laser beam passes, thedeposited molten anti-corrosion surface layer material consolidates andsolidifies, forming the anti-corrosion surface layer 7.

Various ways of scanning the laser beam and delivering the flow of thepowdered anti-corrosion surface layer material may be envisioned,including tilting the laser beam to produce an elongate beam spot 14 foroptimizing the melting of the powdered anti-corrosion surface layermaterial, as shown more clearly in FIGS. 1A and 1B. In one set-up, thelaser optic assembly 4 and the conduit 5 are stationary, and the plates8 and 9 move with the support in a direction that is opposite thedirection indicated by the black arrow 12. In an alternative set-up, thesupport is stationary and the laser optic assembly 4 and the conduit 5are moved in the direction indicated by the black arrow 12. Optionally,the laser optic assembly 4 does not undergo translational movement, butrather a mirror or other beam-directing element is used to scan a laserbeam spot in the direction that is indicated by the black arrow 12, andthe outlet end of the conduit 5 follows the position of the beam spot.Alternatively, the support is used to move the plates 8 and 9 in adirection that is opposite the direction indicated by arrow 12, whilstthe laser optic assembly 4 and the conduit are moved in the directionindicated by the arrow 12.

It is to be understood that the process described above provides ananti-corrosion surface layer along one side of the weld joint 6. Sincethe laser welding process results in the formation of a weld bead onboth sides of the plates 8 and 9, it is desirable to also provide ananti-corrosion surface layer along the opposite side of the weld joint6. As such, the protective-layer forming step should be repeated toprovide the anti-corrosion surface layer along the opposite side of theweld joint 6. Either the laser optic assembly 4 and conduit 5 arerepositioned along the opposite side of the weld joint 6, or thewelded-together plates 8 and 9 are “flipped over” such that the oppositeside of the weld joint 6 faces toward the laser optic assembly 4 and theconduit 5.

The two-step process that is described above may be carried out at asingle workstation, and the same laser optics assembly 4 and lasersource 10 may be controlled to perform both the laser welding step andthe protective-layer forming step. Advantageously, both steps may beperformed at the same workstation, resulting in decreased labor costsand better utilization of floor space. The welds that are produced usingthe two-step process described above have improved corrosion resistance,and it is possible to alter or tailor the mechanical properties of thelaser welds to better match the materials that are being joined. Ofcourse, the use of powdered anti-corrosion surface layer materialsrequires adequate safety equipment and additional cleanup due to unusedpowder that may be deposited on the work pieces and in the immediateworking environment.

The two-step process described above may be performed in combinationwith other laser welding methods, which have been described previously.For instance, when AlSi coated plates are used the laser welding stepmay be performed with the addition of an alloying element (e.g.,titanium or nickel) in order to form a compound in the melt pool with atleast some of the aluminum that enters the melt pool from the AlSilayer. The addition of alloying elements is described in U.S.Provisional Patent Application 62/051,573, which was filed on Sep. 17,2014 and is entitled “Methods of Laser Welding Coated Steel Sheets withAddition of Alloying Elements,” the entire contents of which areincorporated herein by reference. Optionally or alternatively, prior toperforming the laser welding step, the pre-coat layer 3 may be removedfrom the target weld area between the plates 8 and 9 according to theprocess that is described in U.S. Provisional Patent Application62/047,915, which was filed on Jun. 19, 2014 and is entitled “Processand System for Forming Butt-Welded Blanks,” the entire contents of whichare incorporated herein by reference.

FIG. 2A shows a localized anti-corrosion surface layer formed on a firstside of a laser weld joint, and FIG. 2B shows an enlarged view of aportion of FIG. 2A. Since the second laser beam-spot size is larger thanthe first laser beam spot-size, the powdered anti-corrosion surfacelayer material forms an anti-corrosion surface layer 7 on the weld joint(not shown in FIGS. 2A and 2B), and overlapping with the pre-coat layers3 on the plates 8 and 9. As such, the an anti-corrosion surface layer 7provides anti-corrosion protection not only along the weld joint, butalso within regions adjacent to the weld joint in which the pre-coatmaterial 3 has been disrupted. Since the anti-corrosion surface layer 7is formed subsequent to laser welding, the layer 7 covers regionsadjacent to the weld joint in which the pre-coat material has beendisrupted either as a direct result of the laser welding step, or as aresult of a pre-laser welding preparation step that is performed priorto laser welding, such as described in U.S. Provisional PatentApplication 62/047,915 discussed supra.

FIG. 3A shows a localized anti-corrosion surface layer formed on asecond side of a laser weld joint that is opposite the first side shownin FIG. 2A, and FIG. 3B shows an enlarged view of a portion of FIG. 3A.The anti-corrosion surface layer 7′ shown in FIGS. 3A and 3B issubstantially identical to the anti-corrosion surface layer 7 shown inFIGS. 2A and 2B.

FIG. 4 is a cross-sectional view taken along the line A-A in FIG. 1, andshowing a localized anti-corrosion surface layer 7 on a laser weld joint6. As shown in FIG. 4, the thickness of the layer 7 is greater than thethickness of the original pre-coat layer 3 on each of the plates 8 and9. For instance, the thickness of the layer 7 is up to about 0.1 mm,whilst the thickness of the original pre-coat layer 3 is about 20 μm.The thickness of the layer 7 may be controllably varied, e.g., to meetthe specific requirements for different applications. By way of a fewspecific and non-limiting examples, the thickness of the layer 7 may bevaried by varying one or both of the rate of powder deposition (i.e.,the flow rate at which the powdered anti-corrosion surface layermaterial is provided via the conduit 5) and the particle size of thepowdered anti-corrosion surface layer material. The localizedanti-corrosion surface layer 7 may be modified after it is initiallyformed. For instance, subsequent heating of the welded together plates 8and 9, either as part of a separate forming operation or as an extensionof the above-described protective layer forming step, to a temperaturethat is above the melting temperature of the anti-corrosion surfacelayer material but below the melting temperature of the substrates 1 and2, results in melting and redistribution of the anti-corrosion surfacelayer material. In this way, the thickness of the layer 7 may be mademore uniform. Additionally, the melted anti-corrosion surface layermaterial may flow into unprotected regions and thereby form a morecomplete anti-corrosion layer.

Of course, the process that is described in accordance with the variousembodiments of the invention may be modified for use with joiningtechniques other than laser welding. In particular, riveting is amechanical fastening process for joining together sheet metal plates,which results in damage occurring to protective layers on the sheetmetal plates. The process that is described above may be adapted to jointhe sheet metal plates together by riveting in a first step, followed byperformance of the protective-layer forming step. In this alternateembodiment, the laser optic assembly 4 is used only during theprotective layer forming step. For instance, the laser optic assembly 4scans a laser beam over a target area that is to be protected with ananti-corrosion surface layer, whilst a flow of the anti-corrosionsurface layer material is provided via the conduit 5. The spot-size ofthe laser beam is selected to melt the anti-corrosion surface layermaterial but not the material of the rivet or the substrates 1 and 2.

Similarly, the process that is described above may be adapted for thecasting of one piece around another piece with an anti-corrosion surfacelayer. The casting process may damage the anti-corrosion layer on theother piece, making the component susceptible to corrosion. As such, theprotective layer forming step as described above may be performedsubsequent to casting. Once again, the laser optic assembly 4 is usedonly during the protective layer forming step. For instance, the laseroptic assembly 4 scans a laser beam over a target area that is to beprotected with an anti-corrosion surface layer, whilst a flow of theanti-corrosion surface layer material is provided via the conduit 5. Thespot-size of the laser beam is selected to melt the anti-corrosionsurface layer material but not the material of the cast piece or thesubstrate of the other piece.

It is also to be understood that in FIG. 1 the plates 8 and 9 are shownin an arrangement for forming a butt weld joint. Optionally, the plates8 and 9 are arranged one relative to the other to form a different typeof weld joint, such as for instance a lap weld joint.

While the above description constitutes a plurality of embodiments ofthe present invention, it will be appreciated that the present inventionis susceptible to further modification and change without departing fromthe fair meaning of the accompanying claims.

What is claimed is:
 1. A process for laser welding together sheet metalplates, the sheet metal plates each having an anti-corrosion surfacelayer pre-coat, the process comprising: arranging the sheet metal platesone relative to the other and such that an edge of one of the plates isadjacent to and in contact with an edge of another one of the plates;using a first laser beam having a first beam spot-size, forming a laserweld joint along the adjacent edges of the sheet metal plates; andsubsequent to forming the laser weld joint, forming a localizedanti-corrosion surface layer at least on the laser weld joint,comprising: scanning a second laser beam having a second beam spot-sizein a scanning direction along the laser weld joint, wherein the secondbeam spot-size larger than the first beam spot-size; tilting the secondlaser beam in a tilt direction to produce an elongated beam spot; duringthe scanning, providing a flow of a powdered anti-corrosion surfacelayer material toward a portion of the laser weld joint that is beingirradiated by the laser beam, wherein the powdered anti-corrosionsurface layer material is melted by the laser beam and forms a layeradhering to the laser weld joint; and wherein the tilt direction isparallel to the scanning direction.
 2. The process according to claim 1,wherein the anti-corrosion surface layer material is zinc or analuminum-silicon alloy (AlSi).
 3. The process according to claim 1,wherein the sheet metal plates comprise a steel substrate, and whereinthe second beam spot-size is selected to heat the powderedanti-corrosion surface layer material to a temperature that is below themelting temperature of the steel substrate and above 400° C.
 4. Theprocess according to claim 1, wherein the localized anti-corrosion layerextends beyond the edges of the laser weld joint and overlaps with theanti-corrosion surface layer pre-coat on each of the sheet metal plates.5. The process according to claim 1, wherein the laser weld jointextends between a first side of the sheet metal plates and a second sideof the sheet metal plates that is opposite the first side, and whereinthe localized anti-corrosion surface layer is formed at least on thelaser weld joint along each of the first side and the second side. 6.The process according to claim 1, comprising: selecting a flow rate ofthe powdered anti-corrosion surface layer material for forming alocalized anti-corrosion surface layer having a predetermined thickness;and during the scanning, providing the powdered anti-corrosion surfacelayer material at the selected flow rate.
 7. The process according toclaim 1, comprising: selecting a particle size of the powderedanti-corrosion surface layer material for forming a localizedanti-corrosion surface layer having a predetermined thickness; andduring the scanning, providing the powdered anti-corrosion surface layermaterial having the selected particle size.
 8. The process according toclaim 1, wherein the localized anti-corrosion surface layer has athickness that is sufficient for corrosion protection.
 9. The processaccording to claim 1, wherein a single laser head is used to generatethe laser beam having the first beam spot-size and to generate the laserbeam having the second beam spot-size.
 10. The process according toclaim 1, wherein a first laser head is used to generate the laser beamhaving the first beam spot-size and a second laser head is used togenerate the laser beam having the second beam spot-size.
 11. Theprocess according to claim 1, comprising subsequent to forming thelocalized anti-corrosion surface layer, heating the laser welded sheetmetal plates to a temperature that is higher than the meltingtemperature of the anti-corrosion surface layer material, whereby thesubsequent heating causes the anti-corrosion surface layer material tomelt and redistribute over a larger area.
 12. The process according toclaim 1, comprising, prior to forming the laser weld joint, removing theanti-corrosion surface layer pre-coat along the adjacent edges of eachof the sheet metal plates.
 13. The process according to claim 1, whereinthe sheet metal plates form one of a part of a multi-piece body side foran automobile, a part of a multi-piece part for an automobile and a partof a door ring for an automobile.
 14. A process for joining togethermetallic parts, comprising: joining together a first metallic part and asecond metallic part at a joining region, at least one of the firstmetallic part and the second metallic part having an anti-corrosionsurface layer pre-coat, and wherein the surface layer pre-coat isdisrupted within the joining region during the joining; and forming alocalized anti-corrosion surface layer within a target area that is atleast one of within the joining region and adjacent to the joiningregion, comprising: scanning a laser beam having a predetermined beamspot-size along a scanning direction through the target area; tiltingthe laser beam having the second beam spot-size in a tilt direction toproduce an elongated beam spot; during the scanning, providing a flow ofa powdered anti-corrosion surface layer material toward a portion of thetarget area that is being irradiated by the laser beam, wherein thepowdered anti-corrosion surface layer material is melted by the laserbeam and forms a layer adhering to surfaces within the joining region;and wherein the tilt direction is parallel to the scanning direction.15. The process according to claim 14, wherein the joining comprisesjoining using mechanical fasteners.
 16. The process according to claim14, wherein the anti-corrosion surface layer material is zinc or analuminum-silicon alloy (AlSi).
 17. The process according to claim 14,wherein the first and second metallic parts each comprise a steelsubstrate, and wherein the predetermined beam spot-size is selected toheat the powdered anti-corrosion surface layer material to a temperaturethat is below the melting temperature of the steel substrate and above400° C.
 18. The process according to claim 14, wherein the target areaextends away from the joining region and overlaps with adjacent surfacelayer pre-coat that is other than disrupted during the joining.
 19. Theprocess according to claim 14, wherein the joining disrupts the surfacelayer pre-coat along a first side of the sheet metal plates and along asecond side of the sheet metal plates that is opposite the first side,and wherein the target zone comprises a first target zone along thefirst side and a second target zone along the second side.
 20. Theprocess according to claim 14, comprising: selecting a flow rate of thepowdered anti-corrosion surface layer material for forming a localizedanti-corrosion surface layer having a predetermined thickness; andduring the scanning, providing the powdered anti-corrosion surface layermaterial at the selected flow rate.
 21. The process according to claim14, comprising: selecting a particle size of the powdered anti-corrosionsurface layer material for forming a localized anti-corrosion surfacelayer having a predetermined thickness; and during the scanning,providing the powdered anti-corrosion surface layer material having theselected particle size.
 22. The process according to claim 14,comprising subsequent to forming the localized anti-corrosion surfacelayer, heating the joined together metallic parts to a temperature thatis higher than the melting temperature of the anti-corrosion surfacelayer material, whereby the subsequent heating causes the anti-corrosionsurface layer material to melt and redistribute over a larger area. 23.The process according to claim 14, wherein the joining comprises laserwelding.
 24. The process according to claim 23, comprising, prior tolaser welding, removing the anti-corrosion surface layer pre-coat alongedges of the metallic parts that are to be welded together.
 25. Theprocess according to claim 23, wherein the localized anti-corrosionlayer extends beyond the edges of the laser weld joint and overlaps withthe anti-corrosion surface layer pre-coat on each of the sheet metalplates.
 26. The process according to claim 23, wherein the laser weldjoint extends between a first side of the sheet metal plates and asecond side of the sheet metal plates that is opposite the first side,and wherein the localized anti-corrosion surface layer is formed atleast on the laser weld joint along each of the first side and thesecond side.
 27. The process according to claim 23, wherein a singlelaser head is used to generate the laser beam having the first beamspot-size and to generate the laser beam having the second beamspot-size.
 28. The process according to claim 23, wherein a first laserhead is used to generate the laser beam having the first beam spot-sizeand a second laser head is used to generate the laser beam having thesecond beam spot-size.
 29. The process according to claim 23, comprisingsubsequent to forming the localized anti-corrosion surface layer,heating the laser welded sheet metal plates to a temperature that ishigher than the melting temperature of the anti-corrosion surface layermaterial, whereby the subsequent heating causes the anti-corrosionsurface layer material to melt and redistribute over a larger area. 30.The process according to claim 23, comprising, prior to forming thelaser weld joint, removing the anti-corrosion surface layer pre-coatalong the adjacent edges of each of the sheet metal plates.
 31. Theprocess according to claim 23, wherein the sheet metal plates form oneof a part of a multi-piece body side for an automobile, a part of amulti-piece part for an automobile and a part of a door ring for anautomobile.